Halogen-free blowing agents that include cycloaliphatic hydrocarbons and are suitable for isocyanate-based polymeric foams

Abstract: A halogen-free blowing agent is used to produce isocyanate-based polymeric foams. The blowing agent is an organic liquid which is free from halogens and contains a positive binary azeotrope having a minimum boiling temperature in the range of about 15°C to about 80°C at normal atmospheric pressure. Particularly preferred is a binary azeotrope of an alicyclic hydrocarbon such as cyclopentane or cyclohexane and methyl formate. The halogen-free blowing agents contemplated herein provide the following advantages: no ozone depletion potential, no global warming potential, direct replacement in foam formulations for trichloromonofluoromethane (CFC-11), relatively higher blowing action, relatively lower foam density, relatively lower thermal conductivity, better compatibility, and relatively lower materials cost.

Description: Field of the Invention This invention relates to the manufacture of isocyanate based polymeric foams using a halogen-free azeotrope of specific type as a blowing agent. Background of the Invention Polymeric foams are made using a blowing agent that generates a cellular structure as polymerization of reactants takes place. Trichloromonofluoromethane (CFC-11) has been the most often used physical blowing agent for various isocyanate-based polymeric foams, such as polyurethane foams, polyisocyanurate foams, polyurea foams, and polyamide foams, the hybrid foams, as well as for thermoplastic foams, e.g., polystyrene foams, polyethylene foams, polypropylene foams and phenolic foams. However, due to the well-recognized ozone depletion problem in the stratosphere, all kinds of chlorofluorocarbons (CFCs) must be phased out by the end of 1995 according to a worldwide regulation. To achieve that end, some CFC-free, alternative physical blowing agents have been developed in recent years, albeit with limited success. Chemical (or reactive) blowing agents such as water, which generates carbon dioxide gas by the reaction with isocyanate groups, constitute one class of such CFC-free blowing agents. However, water has the following disadvantages as the blowing agent for rigid foams: a relatively high exotherm which may cause scorching, high system viscosity, higher K-factor, poor adhesion to metal substrates due to thinner skin formation, lower dimensional stability (shrinkage), etc. In the case of flexible foams, disadvantages of water as a blowing agent include: relatively high exotherm which may cause discoloration and possible fire risk, and higher system viscosity. Furthermore, integral skin foam preparation is very difficult with such blowing agents, and therefore specific, costly polyols are required. Other chemical blowing agents include enolizable compounds (K. Ashida, International Progress in Urethanes , Eds., Ashida, K. Frisch, K.C., Technomic Publishing Co., Inc. [1980], p. 153), polycarboxylic acids (U.S. Patent No. 5,057,547 to Doerge), specific aldehydes or ketones (U.S. Patent No. 5,079,271 to Gillis). Physical (or non-reactive) blowing agents constitute another class of alternative blowing agents. Such physical blowing agents exhibit ozone depletion potential (ODP) and include the HCFCs (hydrochlorofluorocarbons, e.g., HCFC 141b, CCl 2 FCH 3 ), the HFCs (hydrofluorocarbons, e.g., HFC-356, C 4 H 4 F 6 ), the PFCs (pefluorohydrocarbons, e.g., PF-5050, C 5 F 12 ) and the HFCEs (hydrofluorocarbon ethers, e.g., E-245, CF 3 CH 2 OCH 3 ). A physical blowing agent performs a blowing action by the exothermic reaction of polymer formation. Therefore, the lower the boiling point of the blowing agent, the lower the resulting foam density for the same mole amount of blowing agent. In order to obtain low density foams, a low boiling point liquid is desired. In addition, their raw materials costs are higher than those of other alternative blowing agents, and therefore, their potential for commercial applications is questionable. Recently, n-pentane and cyclopentane have been used in European countries as physical blowing agents for rigid urethane foams (see, for example, E.E. Ball, Proceedings of the Polyurethanes World Congress 1993, Vancouver, Canada, Oct. 10-13, 1993, p. 10). However, due to their non-polarity or relatively low compatibility with other ingredients, special foaming formulations are required for this application. Methylene chloride is another widely used blowing agent for flexible urethane foams, usually as a co-blowing agent with water. However, it is not suitable for use with rigid urethane foams due to a variety of processing problems, e.g., foam collapse or coarse cell foams. Therefore, no commercial applications have been reported to date. A blend of methylene chloride and pentane also has been used for polyisocyanurate foam preparation (U.S. Patent No. 4,898,893 to Ashida). However, this blowing agent encounters problems in preparation of rigid polyurethane foams, such as foam collapse, coarse cells, or open cell structure. Another type of physical blowing agent that has been used is liquid carbon dioxide (U.S. Patent No. 5,120,770 to Doyle et al.). This blowing agent has a disadvantage in that a high pressure foaming equipment is required. The use of acetone/cyclopentane combinations having a cyclopentane:acetone volume ratios between 85:15 and 60:40 as a blowing agent for rigid urethane foams is shown in U.S. Patent No. 3,558,531 to Solyer. However, the obtained foam densities are undesirably higher than those of CFC-11 blown foams. Also known as blowing agents are halogen-containing azeotropes such as 2-methylbutane and HCFC141b (1,1-dichloro-1-fluoroethane), mentioned in U.S. Patent No. 5,057,547 to Doerge, and such as trichlorofluoromethane and methyl formate disclosed in Proceedings of SPI 33rd annual Polyurethane Technical/Marketing Conference, Sept. 30 - Oct.3, 1990, p. 82. However, these latter two kinds of azeotrope contain halogens and thus have the drawback of presenting an ODP problem as well. EP-A-0 421 269 relates to the preparation of rigid polyurethane foams using blowing agents containing cyclopentane or cyclohexane, in combination with low boiling compounds such as dialkyl ethers or cycloalkylen ethers (claims 1 and 2). Among the latter compounds, diethyl ether and furan have been mentioned (column 11, lines 26-27 and Example 3). The polyurethanes can be modified by carbodiimide or isocyanurate groups (column 5, lines 54-57). The blowing agent composition should have a boiling point from 0°C to 50°C (column 11, lines 29-35). Summary of the Invention According to the invention a process of making an isocyanate-based polymeric foam is provided which is characterized by the use of a halogen-free organic liquid as a physical blowing agent for said foam; said organic liquid containing a positive azeotrope having a minimum boiling temperature in the range of 15°C to 80°C at normal atomospheric pressure and constituted by (A) a cycloaliphatic hydrocarbon containing at least 5 but no more than 7 carbon atoms and (B) a compound selected from the group consisting of methyl formate, ethyl formate, methyl acetate, 2-butanone and mixtures thereof. A halogen-free blowing agent that includes a cycloaliphatic hydrocarbon is used in the production of isocyanate-based polymeric foams. The foams are produced with concurrent foaming of reactants by the action of an organic liquid which is a positive azeotrope having a minimum boiling temperature in the range of 15°C to 80°C at normal atmospheric pressure. The azeotropic component blend ratio of the organic liquid usually is in a range of ±20 weight percent from that of an ideal azeotrope. Foam formulations previously used with trichloromonofluoromethane (CFC-11) are well suited for practicing the present invention. By the use of halogen-free blowing agent, the present invention offers the advantages of zero ozone depletion potential (ODP), zero global warming potential (GWP), and compared to CFC-11, a relatively higher blowing efficiency as well as a relatively lower raw material cost. Furthermore, the azeotropes contemplated by the present invention as blowing agents provide foams having relatively lower thermal conductivity than the foams blown with the respective individual components of the azeotrope. Description of Preferred Embodiments The isocyanate-based polymeric foams can be polyurethane foams, polyisocyanurate foams, polyurea foams, polyoxazolidone foams, and the like, prepared according to formulations and processing techniques well known in the art. For example, polyurethane foams are made by the reaction of a polyisocyanate with a polyol as foaming ingredients that are foamed concurrently by the action of a blowing agent. The present invention contemplates the use of halogen-free organic liquids as physical blowing agents for the aforementioned isocyanate based polymeric foams. These organic liquids contain positive azeotropes that have a minimum boiling temperature in the range of 15°C to 80°C at normal atmospheric pressure. Boiling points below 15°C are undesirable because they cause handling problems during processing, e.g., material loss by evaporation due to relatively higher vapor pressure. Boiling points in excess of 80°C reduce blowing efficiency and may cause undesirably high density. A minimum boiling temperature in the range of 15°C to 45°C at normal atmospheric pressure is preferred. Particularly preferred minimum boiling temperature at normal atmospheric pressure is in the range of 20°C to 40°C. The halogen-free blowing agent contemplated by the present invention is an organic liquid constituted by compounds that together form a positive azeotrope, that is, a minimum boiling azeotrope. The compounds that together form the desired azeotrope are a cycloaliphatic hydrocarbon containing at least 5 but no more than 7 carbon atoms and a member of the group consisting of methyl formate, ethyl formats, methyl acetate, 2-butanone and mixtures thereof. The cycloaliphatic (or alicyclic) hydrocarbon containing at least 5 but no more than 7 carbon atoms can be saturated or unsaturated. Illustrative saturated cycloaliphatic hydrocarbons are cyclopentane, methylcyclopentane, cyclohexane and methylcyclohexane. Illustrative unsaturated cycloaliphatic hydrocarbons are cyclopentene, cyclohexene, and 1,3-cyclohexadiene. Examples of the ideal azeotrope blend ratios (by weight) and the boiling points thereof are as follows: cyclopentane/methyl formate = 33.9/66.1 (B.P.=26°C), cyclopentane/methyl acetate = 62.1/37.9 (B.P.=43.2°C), cyclopentene/methyl acetate = 72.3/27.7 (B.P.=41.7°C), cyclopentane/ethyl formate = 45/55 (B.P.=42°C), cyclohexane/2-butanone = 60/40 (B.P.=73°C), cyclohexene/2-butanone = 53/47 (B.P.=73°C). The blend ratio of the blowing agent to be used in the present invention can be within a relatively wide range. The present process is not restricted to the use of only ideal azeotropes of the type described herein. The weight ratio of the azeotropic constituents in the organic liquid utilized as the blowing agent can be within a deviation range from ideal as wide as plus or minus 20 percent (+/- 20%). Preferably, the deviation range is no more than plus or minus 10 percent (+/- 10%), more preferably no more than plus or minus 5 percent (+/- 5%) from the ideal azeotrope composition. For example, while in the case of the cyclopentane/methyl formate azeotrope, the ideal azeotropic blend ratio is 33.9/66.1, for use as a blowing agent for foam preparation the blend ratio can be, respectively, as wide as 14/86 to 54/46, preferably 24/76 to 44/56, more preferably 29/71 to 39/61 Examples of specific binary azeotropes contemplated for use as blowing agents for practicing the present invention are: cyclopentane/methyl formate cyclopentane/ethyl formate cyclopentane/methyl acetate cyclopentane/2-butanone cyclopentene/methyl formate cyclopentene/ethyl formate cyclopentene/methyl acetate cyclopentene/2-butanone methylcyclopentane/ethyl acetate cyclohexane/methyl formate cyclohexane/ethyl formate cyclohexane/methyl acetate cyclohexane/ethyl acetate cyclohexane/2-butanone cyclohexene/methyl formate cyclohexene/ethyl formate cyclohexene/methyl acetate cyclohexene/2-butanone methylcyclohexane/2-butanone 1,3-cyclohexadiene/ethyl acetate The advantages of the use of azeotropic and/or azeotrope-containing blend solvents as the blowing agent for isocyanate based polymeric foams as contemplated by the present invention are as follows: (1) The azeotrope to be used has a minimum boiling point and thus gives more efficient blowing action; therefore, relatively lower density foams can be obtained. (2) The azeotrope blowing agents have proper polarity, and result in better compatibility with foaming ingredients; therefore, finer cell foams can be obtained than by the use of a single alkane blowing agent. Polarity extremes of individual blowing agent components can be balanced and, as a result, foam cell structure is improved. (3) Due to the similarity of boiling point and/or polarity of the azeotrope with that of CFC-11, the azeotrope can directly replace CFC-11 without any change in the conventional raw materials for CFC-11 based formulations. Special formulation studies to effect such substitution are not needed. This is a significant commercial advantage and saves system development costs as well as time. For example, integral skin foams are widely used for automotive interior parts. Due to the ODP problem, these foams are now prepared using water as a blowing agent with expensive, special raw materials and special facilities. The use of the azeotrope blowing agent in accordance with the present invention in conventional integral skin formulations provides good integral skin foams without any problems. Conventional raw materials, formulations, and processing conditions that are the same as or very similar to those employed for CFC-11 blown integral skin foams can be readily used. CFC-11-based formulations for rigid urethane foams and isocyanurate foams can also be used by the direct replacement of the azeotrope blowing agent for CFC-11. (4) Another big advantage of the azeotrope blown foams lies in the fact that the resulting foams have lower thermal conductivity than that of respective components of the azeotrope as can be seen in Example 5. (5) Further advantage is the relatively lower cost of azeotrope-based foam systems. In principle, the foam density is proportional to the number of moles of blowing agent employed. The azeotropes contemplated by the present invention have a lesser molecular weight than that of CFC-11 and other fluorinated alternative blowing agents such as HCFCs, HFCs, and PFCs. Therefore, azeotrope-blown foams according to the present invention need a smaller amount of blowing agent to produce comparable foam density. In addition, the unit cost of the azeotrope is less than that of the fluorinated alternative blowing agents. The isocyanate based polymeric foams prepared in accordance with the present invention are prepared by the substantially simultaneous formation of polyisocyanate-derived polymers and gas generation The isocyanate based polymeric foams include polyurethane foams, polyurea foams, polyisocyanurate foams, polyoxazolidone foams, polyamide foams, polyimide foams, polycarboiimide foams, and hybrid foams thereof. Polyurethane foams are prepared by the addition reaction of a polyisocyanate and a polyol in the presence of the presently contemplated halogen-free azeotropic blowing agent, a surfactant, a catalyst, and an additive such as a nucleating agent, if necessary. The choice of polyol and polyisocyanate results in a variety of foam properties, including flexible foams, integral skin flexible foams, semi-rigid foams, rigid foams, and others. Various isocyanate-based polymer foams including polyurethane foams, polyurea foams, modified polyisocyanurate foams, polyoxazolidone foams, polyamide foams, polyimide foams and polycarbodiimide foams have been described by in detail in D. Klempner and K.C. Frisch, eds., Polymeric Foams , Chapter 6 by K. Ashida, Hanser Publications (1991). Polyurea foams are prepared by the reaction of polyisocyanate with amine-terminated polyethers in the presence of the presently contemplated blowing agent, surfactant, and, if necessary, a cross linker and/or a catalyst. Polyisocyanurate foams can be prepared by the cyclotrimerization of isocyanate groups in the presence of the presently contemplated blowing agent, a cyclotrimerization catalyst, a surfactant and a modifier. The modifier can be at least one of a polyol, a polyepoxide, a polycarboxylic acid, a polyamine, a secondary aromatic diamine, or the like. Urethan-modified isocyanurate foams are the most representative type of the modified isocyanurate foams and are described in U.S. Patent No. 3,625,872 to Ashida. Polyoxazolidone-modified isocyanurate foams are disclosed in U.S. Patent No. 3,793,236 to Ashida et al. Polyamide-modified isocyanurate foams are disclosed in French Patent No. 1,511,865. Urea-modified isocyanurate foams are disclosed in Proceedings of the SPI-34th Technical/Marketing Conference, Oct. 21-24, 1992, at p. 331. Unmodified polyamide foams can be prepared by the reaction of isocyanate groups with carboxylic group-terminated polyester oligomers in the presence of a catalyst, and a surfactant. A blowing agent is not needed because the amide formation is accompanied by the generation of carbon dioxide gas. However, isocyanate-terminated polyesters having amide linkages, i.e., isocyanate-terminated prepolymer, can be used for making foams in the presence of a physical blowing agent of the type contemplated by the present invention, a surfactant, and a catalyst. Unmodified polyimide foams can be prepared by the reaction of isocyanate-groups with a carboxylic acid dianhydride in the presence of a catalyst, and a surfactant but without a blowing agent, because the imide formation is accompanied with the evolution of carbon dioxide gas. Similarly, polycarbodiimide foams can be prepared by the polycondensation of isocyanate groups with the simultaneous generation of carbon dioxide in the presence of a surfactant and a catalyst. However, isocyanate-terminated linear prepolymers can be further reacted to form carbodiimide foams or carbodiimide-containing isocyanurate foams. These cases need a physical blowing agent, and the presently contemplated blowing agents are eminently well suited for this purpose. Isocyanate-based hybrid foams include polyurethane-polyisocyanurate foams, polyoxazolidone-polyisocyanurate foams, polyurethane-polyimide foams, polyamide-polyurethane foams, and the like. Examples of isocyanate-based hybrid foams include polyurethane/unsaturated polyester foams, and polyurethane/vinyl ester foams which are described in U.S. Patent No. 5,091,436 to Frisch. The polyurethane foam manufacture in general is well known in the art and is described in many books, such as Polyurethanes, Chemistry and Technology , Part 1, and Part 2, by J.H. Saunders and K.C. Frisch, Interscience Publishers (1962), Polyurethane Handbook , Edited by Guenther Oertel, Carl Hanser Verlag (1985), The ICI Polyurethane Book , 2nd Edition, Edited by George Woods, John Wiley & Sons (1990), Flexible Polyurethane Foams , Edited by R. Herrington, and Hock, The Dow Chemical Company (1991), Handbook of Polymeric Foams and Foam Technology , Edited by D. Klempner and K.C. Frisch, Hanser Publishers (1991). The isocyanate based polymeric foam systems are composed of at least two components. The azeotrope-containing blowing agent can be added into either component, because of non-reactivity with the ingredients. For example, in the case of urethane foams, the azeotrope-containing blowing agents can be added into either one of the polyol and polyisocyanate components, or into both components. A nucleating agent can be added to any foam formulation, if desired, for producing foams having relatively finer cells. The amount of nucleating agent that can be added is in a range of about one to ten percent by weight per 100 parts of total foaming ingredients. Some examples of suitable nucleating agents are ultra-fine powders, e.g., 1-5 microns in size, of polyethylene, polypropylene or silica, as well as liquid state nucleating agents, e.g., perfluoroalkanes, such as C 5 F 12 , C 6 F 14 , C 7 F 16 , C 5 F 11 NO, which can be emulsified in the foaming ingredients. The resulting foams have very fine cells; therefore, higher insulating properties can be achieved. The present invention is further illustrated by the examples that follow. EXAMPLES 1 & 2 Foams were prepared by the cup foaming procedure using a drill mixer. Pure cyclopentane and industrial grade cyclopentane, respectively, were utilized as the blowing agents. Formulation (pbw) Example 1 Example 2 Polyether polyol 300 300 Silicone surfactant 4.5 4.5 t-Amine catalyst 6.0 6.0 Dibutyltin dilaurate 0.9 0.9 Cyclopentane 16.2 0 Industrial grade cyclopentane 0 16.2 Methyl formate 31.2 31.2 Polymeric isocyanate 271 271 Foam Properties Density, kg/m 3 34.5 31.3 lb/cu.ft. 2.15 1.95 Thermal Conductivity, mW/(m·K) 24.4 24.3 EXAMPLES 3 A cyclopentane-based binary azeotrope was used as blowing agent while preparing a foam using the same technique as in Examples 1 and 2, above. Formulation (pbw) Example 3 Polyether polyol 200 Silicone surfactant 3.0 t-Amine catalyst 2.0 Dibutyltin dilaurate 0.3 Cyclopentane 22.6 Methyl acetate 13.6 Polymeric isocyanate 181 Moles of blowing agent/100g of polyol 0.25 Foam Properties Density, kg/m 3 32.5 Thermal Conductivity, mW/(m·K) 25.8 EXAMPLE 4 Cyclopentene, an unsaturated alicyclic hydrocarbon, was used with methyl acetate as blowing agent while preparing foams using the technique as in Examples 1 and 2, above. Formulation (pbw) Polyether polyol 100 Silicone surfactant 1.5 t-Amine catalyst 2.0 Dibutyltin dilaurate 0.3 Cyclopentene 12.6 Methyl acetate 4.8 Polymeric isocyanate 90.3 Moles of blowing agent/100g of polyol 0.25 Foam Properties Density, kg/m 3 30.2 EXAMPLE 5 Foams were prepared at various blend ratios of cyclopentane to methyl formate by the cup foaming technique and using a drill mixer. The following data show the effect of blend ratio of cyclopentane/methyl formate on the density and the thermal conductivity of the resulting foams. The amount of blowing agent was kept constant at 0.25 mole/100 g of polyol. Formulation (pbw) Polyether polyol 200 200 200 200 200 200 200 200 200 Silicone surfactant 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 3.0 t-Amine catalyst 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Dibutyltin dilaurate 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Cyclopentane 35.0 31.5 28.0 24.6 21.0 17.6 14.0 10.6 7.0 Methyl formate 0 3.0 6.0 9.0 12.0 15.0 18.0 21.0 24.0 Polymeric isocyanate 181 181 181 181 181 181 181 181 181 Foam Properties Density, kg/m 3 31.2 30.8 30.4 30.1 29.8 29.2 28.5 29.5 Thermal conductivity, mW/(m·K) 27.1 26.1 25.9 25.2 24.5 24.8 25.5 27.3 It was also noted that the thermal conductivity of foams made with cyclopentane/methyl formate azeotrope exhibited a relatively lower thermal conductivity than those made with n-pentane/methyl formate azeotrope as the blowing agent. COMPARATIVE EXAMPLE 6 For comparison purposes, foams were prepared at various blend ratios of cyclopentane to acetone by the cup foaming technique and using a drill mixer. The foam formulation is set forth below. Formulation (pbw) Polyether polyol 100 100 100 100 100 Silicone surfactant 1.5 1.5 1.5 1.5 1.5 t-Amine catalyst 2.0 2.0 2.0 2.0 2.0 Dibutyl dilaurate 0.3 0.3 0.3 0.3 0.3 Cyclopentane 17.7 15.9 14.1 12.4 10.6 Acetone 0 1.5 2.9 4.4 5.8 Polymeric isocyanate 90.3 90.3 90.3 90.3 90.3 Foam Properties Density, kg/m 3 33.5 35.1 35.3 35.6 35.7 lbs/cu.ft 2.09 2.19 2.20 2.22 2.23 All foams had cracks. At over 50 mole percent acetone the resulting foams had large cracks, and density determination was difficult. EXAMPLE 7 Integral skin foams were prepared as shown below, using an azeotrope blowing agent. Mold size: 200 x 200 x 25 mm. Mold temperature: 30°C. Formulation (pbw) Control Example 7 Polyol A 160 160 Polyol B 50 50 1,4-Butanediol 2.0 2.0 t-Amine catalyst 2.2 2.2 CFC-11 27.4 0 Cyclopentane 0 4.4 Methyl formate 0 8.2 Liquid MDI 87.0 87.0 Foam Properties Average Density, kg/m 3 297. 303. lbs/cu.ft 18.6 19.0 Foams having an integral skin with a thickness of about 2 mm were obtained. EXAMPLE 8 Flexible polyurethane foams were prepared by the conventional cup foaming technique using CFC-11 as control, and a blend of cyclopentane/methyl formate, respectively, as blowing agents. Formulation (pbw) Control Example 8 Polyether polyol A 100 100 Silicone surfactant 2.0 2.0 t-Amine catalyst 0.5 0.5 Dibutyltin dilaurate 0.1 0.1 Water 3.0 3.0 CFC-11 14.0 0 Cyclopentane 0 2.2 Methyl formate 0 4.2 TDI (80/20 isomer) 40.7 40.7 Reaction Profile Cream time, sec. 17 16 Rise time, sec. 98 93 Foam Properties Density, kg/m 3 20.5 22.8 lbs/cu.ft 1.28 1.42 EXAMPLES 9, 10 & 11 Urethane-modified isocyanurate foams were prepared by the conventional cup foaming technique using a blend of cyclopentane and methyl formate, or HCFC 141b, as blowing agent as indicated below. Formulation (pbw) Control Example 9 Example 10 Example 11 NCO/OH (Eq. Ratio) 5.0 5.0 10.0 15.0 Polyol 25.3 25.3 12.9 8.57 t-Amine catalyst 1.6 1.6 1.6 1.6 Silicone surfactant 0.7 0.7 0.7 0.7 Water 0.1 0.1 0.1 0.1 HCFC 141b 14.0 0 0 0 Cyclopentane 0 2.6 2.6 2.6 Methyl formate 0 5.0 5.0 5.0 Polymeric isocyanate 73.7 73.7 73.7 73.7 Reaction Profile Cream time, sec. 17 18 18 17 Tack free time, sec. 32 40 36 32 Rise time, sec. 55 68 62 57 Foam Properties Density, kg/m 3 26.2 26.7 29.7 27.3 lbs/cu.ft. 1.64 1.67 1.85 1.70 Tumbling friability, % weight loss 29.3 24.5 34.7 36.2 EXAMPLE 12 Cyclohexane (CHX) / methyl formate (MFT) blends in different blend ratios were used for making foams by the conventional cup foaming technique. The relationship between blend ratio and foam density is noted. Formulation (pbw) Polyether polyol 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 Polyether polyol 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 50.0 Silicone surfactant 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 t-Amine 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 Dibutyltin dilaurate 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 0.05 Cyclohexane 21.0 18.9 16.8 14.7 12.6 10.5 8.4 6.3 4.2 2.1 0 Methyl formate 0 1.5 3.0 4.5 6.0 7.5 9.0 10.5 12.0 13.5 15.0 Polymeric isocyanate 112.6 112.6 112.6 112.6 112.6 112.6 112.6 112.6 112.6 112.6 112.6 Foam Properties Density, kg/m 3 NA NA 39.9 38.6 38.1 37.6 36.5 35.2 34.5 32.6 34.0 Density. lbs/cu.ft. NA NA 2.49 2.41 2.38 2.35 2.28 2.20 2.15 2.04 2.12 Example 13 For the purpose of comparing the properties of the foams for which cyclopentane/methyl formate mixture is used as the foaming agent and of those for which n-pentane/methyl formate mixture is used as the foaming agent, foams were prepared following the formulations below, by the cup foaming technique using a drill mixer. The density and thermal conductivity of the resultant foams were measured, with the results as in the table below the formulations. The thermal conductivity values of the foams as indicated in the table were measured in the direction perpendicular to the foaming direction. Formulation (pbw) CPT/MFT NPT/MFT Polyether polyol 100 100 Water 2 2 Surfactant 2 2 Amine catalyst 1 1 Metal catalyst 0.1 0.1 Cyclopentane 5.5 0 n-Pentane 0 5.6 Methyl formate 3.1 3.1 Polymeric isocyanate 148.9 148.9 Foam Properties Density, kg/m 3 Thermal 35.2 34.8 Conductivity mW/(m·K) 19.9 21.6

Claims: A process of making an isocyanate-based polymeric foam characterized by the use of a halogen-free organic liquid as a physical blowing agent for said foam; said organic liquid containing a positive azeotrope having a minimum boiling temperature in the range of 15°C to 80°C at normal atmospheric pressure and constituted by (A) a cycloaliphatic hydrocarbon containing at least 5 but no more than 7 carbon atoms and (B) a compound selected from the group consisting of methyl formate, ethyl formate, methyl acetate, 2-butanone and mixtures thereof. The process in accordance with claim 1 wherein the foam is a polyurethane foam. The process in accordance with claim 1 wherein the foam is a rigid polyurethane foam. The process in accordance with claim 1 wherein the foam is an integral skin, flexible polyurethane foam. The process in accordance with claim 1 wherein the foam is a modified isocyanurate foam. The process in accordance with claim 1 wherein the foam is a urethane-modified polyisocyanurate foam. The process in accordance with claim 1 wherein said azeotrope has a minimum boiling temperature in the range of 15°C to 45°C. The process in accordance with claim 1 wherein said azeotrope has a minimum boiling temperature in the range of 20°C to 40°C. The process in accordance with claim 1 wherein the cycloaliphatic hydrocarbon is cyclopentane. The process in accordance with claim 1 wherein the azeotrope is a blend of cyclopentane and methyl formate. The process in accordance with claim 1 wherein the azeotrope is a blend of cyclopentane and 2-butanone. The process in accordance with claim 1 wherein the azeotrope is a blend of cyclopentane and methyl acetate. The process in accordance with claim 1 wherein the cycloaliphatic hydrocarbon is cyclopentene. The process in accordance with claim 1 wherein the cycloaliphatic hydrocarbon is cyclohexane. The process in accordance with claim 1 wherein the cycloaliphatic hydrocarbon is cyclohexene. A process of making an isocyanate-based polymeric foam which comprises foaming by action of a halogen-free blowing agent which is a positive azeotrope having a minimum boiling temperature in the range of 15°C to 80°C at normal atomospheric pressure and constituted by (A) a cycloaliphatic hydrocarbon containing at least 5 but no more than 7 carbon atoms and (B) an aliphatic carboxylic acid ester selected from the group consisting of methyl formate, ethyl formate and methyl acetate. The process in accordance with claim 16 wherein said positive azeotrope is constituted by cyclopentane and methyl formate. The process in accordance with claim 16 wherein said positive azeotrope is constituted by cyclopentane and ethyl formate. The process in accordance with claim 16 in which said positive azeotrope is constituted by cyclopentane and methyl acetate. The process in accordance with claim 16 in which said positive azeotrope is constituted by cyclohexane and methyl formate. A process of making an isocyanate-based polymeric foam which comprises foaming by action of a halogen-free blowing agent which is a positive azeotrope having a minimum boiling temperature in the range of 15°C to 80°C and constituted by a cycloaliphatic hydrocarbon containing at least 5 but no more than 7 carbon atoms and 2-butanone. The process in accordance with claim 21 wherein said positive azeotrope is constituted by cyclohexane and 2-butanone. The process in accordance with claim 21 wherein said positive azeotrope is constituted by cyclohexene and 2-butanone. The process in accordance with claim 21 wherein said positive azeotrope is constituted by cyclopentane and 2-butanone. The process in accordance with claim 21 wherein said positive azeotrope is constituted by cyclopentene and 2-butanone. The process in accordance with claim 1 wherein a nucleating agent is also present during foaming. The process in accordance with claim 26 wherein the nucleating agent is perfluoropentane. The process in accordance with claim 26 wherein the nucleating agent is present in an amount in the range of 1 to 10 parts by weight per 100 parts of said foaming ingredients. The process in accordance with claim 1 wherein the weight ratio of azeotropic constituents in said organic liquid is within a deviation range of +/- 20 percent from ideal azeotrope. The process in accordance with claim 1 wherein the weight ratio of azeotropic constituents in said organic liquid is within a deviation range of no more than +/- 10 percent from ideal azeotrope. The process in accordance with claim 1 wherein the weight ratio of azeotropic constituents in said organic liquid is within a deviation range of no more than +/- 5 percent from ideal azeotrope.

Inventors: ASHIDA KANEYOSHI, ASHIDA, KANEYOSHI
Applicants: NISSHIN SPINNING, NISSHINBO INDUSTRIES, INC.
Application year: 1994
Main classification: C08J9
IPC codes: C08J9, C09K3